This invention relates to a replication method for a replica database in a parallel database management system.
In a database replication system, in order to avoid suspension of business due to occurrence of a failure or the like, a computer that performs distribution of data processing tasks and storage of data creates a replica database that is a replica of a master database.
It is necessary that the replica database provides data, whose contents logically match those of the master database, at the time of reference. Therefore, when the master database is updated, it is necessary that the contents of the update are reflected in the replica database. In order to reflect the contents of the update made to the master database in the replica database, a database management system retrieves update information from an update log file, in which the contents of the update made to the master database are recorded, and reflects the contents of the update in the replica database based on the retrieved update information (see JP 2001-175681 A, for instance).
In a parallel database management system based on a Shared-Nothing system in which plural DB access servers are provided and the DB access servers access data areas respectively allocated thereto, the contents of updates made to the data areas respectively allocated to the servers are recorded in update log files that are respectively managed by the servers. Therefore, in order to create a replica of a master database that is managed by the parallel database management system, processing for exporting the updates in a replica database is executed in units of the update log files respectively managed by the DB access servers. In other words, the contents of the updates are imported in the replica database in units of the DB access servers. Through the import processing, the contents of the updates are imported in the replica database in an asynchronous manner.